Cooling device and method of controlling cooling device

ABSTRACT

A cooling device capable of achieving cooling performance suitable for an amount of generated heat from a heat source is provided. A cooling device cooling HV equipment includes a compressor for circulating a coolant; a heat exchanger performing heat exchange between the coolant and outside air; an expansion valve decompressing the coolant; a heat exchanger performing heat exchange between the coolant and air-conditioning air; a cooling unit provided on a route of the coolant flowing between the heat exchanger and the expansion valve, and cooling the HV equipment using the coolant; a bypass route bypassing the expansion valve and the heat exchanger; and a switching valve selectively switching between a flow of the coolant flowing from the cooling unit toward the expansion valve and a flow of the coolant flowing through the bypass route.

TECHNICAL FIELD

The present invention relates to a cooling device and a method ofcontrolling the cooling device, and particularly to a cooling devicecooling a heat source utilizing a vapor compression refrigeration cycleand a method of controlling the cooling device.

BACKGROUND ART

In recent years, as one of countermeasures against environmentalproblems, attention has been paid to a hybrid vehicle, a fuel cellvehicle, an electric vehicle, and the like running with driving force ofa motor. In such vehicles, electric devices such as a motor, agenerator, an inverter, a converter, and a battery generate heat bytransmission and reception of electric power. Accordingly, there is aproposed technique for cooling a heat-generating body utilizing a vaporcompression refrigeration cycle used as an air-conditioning apparatusfor a vehicle.

For example, Japanese Patent Laying-Open No. 2007-69733 (PTD 1)discloses a system for cooling a heat-generating body utilizing acoolant for an air-conditioning device. In the system, a heat exchangerfor performing heat exchange with air-conditioning air and a heatexchanger for performing heat exchange with the heat-generating body arearranged in parallel on a coolant passage extending from an expansionvalve to a compressor. Japanese Patent Laying-Open No. 2005-90862 (PTD2) discloses a cooling system, in which heat-generating body coolingmeans for cooling a heat-generating body is provided on a bypass passagebypassing a decompressor, an evaporator and a compressor in arefrigeration cycle for air-conditioning. Japanese Patent Laying-OpenNo. 2001-309506 (PTD 3) discloses a cooling system, in which a coolantof a refrigeration cycle device for vehicle air-conditioning iscirculated to a cooling member of an inverter circuit portion forperforming a drive control of a vehicle running motor, therebysuppressing cooling of air-conditioning air flow by an evaporator of therefrigeration cycle device for vehicle air-conditioning when cooling ofthe air-conditioning air flow is not required.

As to a vehicle air-conditioning apparatus, Japanese Patent Laying-OpenNo. 2011-1048 (PTD 4) discloses a vehicle air-conditioning system, inwhich a heat storage member of a heat storage unit for a vehicle cabinstores an amount of heat, and the heat storage unit for a vehicle cabinperforms heat exchange of the amount of heat with a heat exchangemedium.

CITATION LIST Patent Document

-   PTD 1: Japanese Patent Laying-Open No. 2007-69733-   PTD 2: Japanese Patent Laying-Open No. 2005-90862-   PTD 3: Japanese Patent Laying-Open No. 2001-309506-   PTD 4: Japanese Patent Laying-Open No. 2011-1048

SUMMARY OF INVENTION Technical Problem

For the purpose of practical use, a hybrid vehicle has been currentlydeveloped so as to allow selection of a driving state from a normaldriving mode and a sport driving mode in which acceleration isprioritized. The sport driving mode is an operation mode in which hybridequipment is operated in a highly loaded state, thereby increasing thedriving force as compared with that in the normal driving mode, toimprove the vehicle running performance. During the operation in thesport driving mode, the amount of heat generated from the hybridequipment operated in the highly loaded state is increased. Accordingly,in order to prevent overheating of the hybrid equipment, it is requiredto develop a technique for temporarily improving the cooling performancefor the hybrid equipment.

The present invention has been made in light of the above-describedproblems. A main object of the present invention is to provide a coolingdevice capable of achieving a cooling performance suitable for theamount of heat generated from a heat source. Another object of thepresent invention is to provide a method of controlling a cooling devicefor achieving a cooling performance suitable for the amount of heatgenerated from a heat source.

Solution to Problem

A cooling device according to the present invention is a cooling devicecooling a heat source, and includes a compressor for circulating acoolant; a first heat exchanger performing heat exchange between thecoolant and outside air; a decompressor decompressing the coolant; asecond heat exchanger performing heat exchange between the coolant andair-conditioning air; a cooling unit provided on a route of the coolantflowing between the first heat exchanger and the decompressor, andcooling the heat source using the coolant; a bypass route bypassing thedecompressor and the second heat exchanger; and a route selection unitselectively switching between a flow of the coolant flowing from thecooling unit toward the decompressor and a flow of the coolant flowingthrough the bypass route.

According to the above-described cooling device, preferably, the coolingdevice includes a temperature lowering unit lowering a temperature ofthe coolant. The temperature lowering unit lowers the temperature of thecoolant flowing through the cooling unit when the route selection unitselects the flow of the coolant flowing through the bypass route. Thecooling device may include an electronic expansion valve provided on aroute of the coolant flowing between the first heat exchanger and thecooling unit.

According to the above-described cooling device, preferably, the coolingdevice includes a gas-liquid separator provided on a route of thecoolant flowing between the second heat exchanger and the compressor.The coolant flowing from the cooling unit through the bypass route flowsinto the gas-liquid separator.

According to the above-described cooling device, preferably, the routeselection unit selects the flow of the coolant flowing through thebypass route when an amount of generated heat by the heat source isincreased.

According to the above-described cooling device, preferably, the coolingdevice includes a communication passage allowing communication between aroute of the coolant flowing between the compressor and the first heatexchanger, and a route of the coolant flowing between the cooling unitand the decompressor.

According to the above-described cooling device, preferably, the routeselection unit can form a flow of the coolant flowing from the coolingunit toward the communication passage.

A method of controlling a cooling device according to the presentinvention is a method of controlling a cooling device cooling a heatsource. The cooling device includes a compressor for circulating acoolant, a first heat exchanger performing heat exchange between thecoolant and outside air, a decompressor decompressing the coolant, asecond heat exchanger performing heat exchange between the coolant andair-conditioning air, a cooling unit provided on a route of the coolantflowing between the first heat exchanger and the decompressor, andcooling the heat source using the coolant, a bypass route bypassing thedecompressor and the second heat exchanger, and a route selection unitselectively switching between a flow of the coolant flowing from thecooling unit toward the decompressor and a flow of the coolant flowingthrough the bypass route. The above-described control method includesthe steps of: determining an amount of generated heat by the heatsource; and cooling the heat source by forming the flow of the coolantflowing through the bypass route when it is determined in the step ofdetermining an amount of generated heat that the amount of generatedheat is equal to or higher than a threshold value.

Preferably, the cooling device includes an electronic expansion valveprovided on a route of the coolant flowing between the first heatexchanger and the cooling unit. In the step of cooling the heat source,an opening degree of the electronic expansion valve is decreased to coolthe heat source.

Preferably, the above-described control method includes the steps of:determining an operation state of the compressor when it is determinedin the step of determining an amount of generated heat that the amountof generated heat is equal to or higher than the threshold value; andstarting the compressor when it is determined in the step of determiningan operation state that the compressor is being stopped.

Advantageous Effects of Invention

According to the cooling device of the present invention, it becomespossible to achieve a cooling performance suitable for the amount ofheat generated from the heat source.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing the configuration of a coolingdevice according to the first embodiment.

FIG. 2 is a Mollier chart showing the state of a coolant in a vaporcompression refrigeration cycle.

FIG. 3 is a schematic diagram showing the cooling device in the casewhere the required cooling performance for HV equipment is raised.

FIG. 4 is a schematic diagram showing the cooling device in the casewhere the required cooling performance for the HV equipment is raisedwhile an air conditioner is stopped.

FIG. 5 is a Mollier chart showing the state of the coolant in the casewhere the required cooling performance for the HV equipment is raised.

FIG. 6 is a schematic diagram showing the configuration of a coolingdevice according to the second embodiment.

FIG. 7 is a diagram showing settings of a compressor and valves for eachoperation mode of the cooling device.

FIG. 8 is a schematic diagram showing the cooling device in the casewhere the vapor compression refrigeration cycle is stopped.

FIG. 9 is a schematic diagram showing the flow of the coolant coolingthe HV equipment while the vapor compression refrigeration cycle isstopped.

FIG. 10 is a schematic diagram showing the cooling device in the casewhere the required cooling performance for the HV equipment is raisedwhile the air conditioner is operated.

FIG. 11 is a schematic diagram showing the cooling device in the casewhere the required cooling performance for the HV equipment is raisedwhile the air conditioner is stopped.

FIG. 12 is a block diagram showing details of the configuration of acontrol unit.

FIG. 13 is a flowchart illustrating an example of a method ofcontrolling the cooling device.

DESCRIPTION OF EMBODIMENTS

The embodiments of the present invention will be hereinafter describedwith reference to the accompanying drawings, in which the same orcorresponding components are designated by the same referencecharacters, and description thereof will not be repeated.

First Embodiment

FIG. 1 is a schematic diagram showing the configuration of a coolingdevice 1 according to the first embodiment. As shown in FIG. 1, coolingdevice 1 includes a vapor compression refrigeration cycle 10. Vaporcompression refrigeration cycle 10 is mounted on a vehicle, for example,to perform cooling in a vehicle cabin. The cooling with use of vaporcompression refrigeration cycle 10 is performed, for example, when aswitch for performing cooling is turned on, or when an automatic controlmode for automatically adjusting the temperature in the vehicle cabin ata set temperature is selected and the temperature in the vehicle cabinis higher than the set temperature.

Vapor compression refrigeration cycle 10 includes a compressor 12, aheat exchanger 14 as the first heat exchanger, a heat exchanger 15, anexpansion valve 16 as an example of a decompressor, and a heat exchanger18 as the second heat exchanger. Vapor compression refrigeration cycle10 also includes a gas-liquid separator 40 arranged on the route of thecoolant between heat exchanger 18 and compressor 12.

Compressor 12 is operated by a motor or an engine mounted on a vehicleas a power source and adiabatically compresses the coolant gas to obtainsuperheated coolant gas. Compressor 12 takes in and compresses a coolantflowing from heat exchanger 18 during operation of vapor compressionrefrigeration cycle 10, and then discharges a high-temperature andhigh-pressure gas-phase coolant to coolant passage 21. Compressor 12discharges the coolant to coolant passage 21 to allow circulation of thecoolant through vapor compression refrigeration cycle 10.

Heat exchangers 14 and 15 allow superheated coolant gas compressed bycompressor 12 to radiate heat isobarically to an external medium toobtain coolant liquid. The high-pressure gas-phase coolant dischargedfrom compressor 12 is condensed (liquefied) by radiating heat to aperiphery of heat exchangers 14 and 15 for cooling. Heat exchangers 14and 15 each include a tube through which the coolant flows, and a finfor performing heat exchange between the coolant flowing through thetube and air around heat exchangers 14 and 15.

Heat exchangers 14 and 15 perform heat exchange between cooling air andthe coolant. The cooling air may be supplied to heat exchangers 14 and15 by natural draft generated by vehicle running. Alternatively, thecooling air may be supplied to heat exchangers 14 and 15 by forced draftfrom a cooling fan such as a condenser fan 42 or a radiator fan forcooling the engine. Condenser fan 42 rotates with the driving forcereceived from motor 44 to generate airflow and supply cooling air toheat exchangers 14 and 15. The heat exchange performed in heatexchangers 14 and 15 lowers the temperature of the coolant to liquefythe coolant.

Expansion valve 16 allows the high-pressure liquid-phase coolant flowingthrough coolant passage 25 to be sprayed from a small pore for expansionto achieve a low-temperature, low-pressure mist-like coolant. Expansionvalve 16 decompresses the coolant liquid condensed by heat exchangers 14and 15 to obtain moist vapor in a gas-liquid mixed state. In addition,the decompressor for decompressing coolant liquid is not limited toexpansion valve 16 performing throttle expansion, but may be a capillarytube.

By evaporation of the mist-like coolant flowing through heat exchanger18, this heat exchanger 18 absorbs heat of ambient air introduced so asto come in contact with heat exchanger 18. Heat exchanger 18 uses thecoolant decompressed by expansion valve 16 to absorb heat ofevaporation, caused when the moist vapor of the coolant is evaporated tobecome coolant gas, from the air-conditioning air flowing into thevehicle cabin, so that the vehicle cabin is cooled. The air-conditioningair with a temperature lowered due to absorption of heat by heatexchanger 18 is returned again into the vehicle cabin, so that thevehicle cabin is cooled. In heat exchanger 18, the coolant absorbs heatfrom its surroundings and is then heated.

Heat exchanger 18 includes a tube through which the coolant flows, and afin for heat exchange between the coolant flowing through the tube andthe ambient air of heat exchanger 18. The coolant in the state of moistvapor flows through the tube. When flowing through the tube, the coolantis evaporated by absorbing heat of the air-conditioning air via the finas latent heat of evaporation, and then turned into superheated vapor bysensible heat. The evaporated coolant flows into compressor 12 viacoolant passage 27. Compressor 12 compresses the coolant flowing fromheat exchanger 18.

Vapor compression refrigeration cycle 10 further includes a coolantpassage 21 allowing communication between compressor 12 and heatexchanger 14, coolant passages 22 and 23 allowing communication betweenheat exchanger 14 and heat exchanger 15, a coolant passage 24 allowingcommunication between heat exchanger 15 and expansion valve 16, acoolant passage 25 allowing communication between expansion valve 16 andheat exchanger 18, a coolant passage 26 allowing communication betweenheat exchanger 18 and gas-liquid separator 40, and a coolant passage 27allowing communication between gas-liquid separator 40 and compressor12.

Coolant passage 21 is a passage for causing the coolant to flow fromcompressor 12 to heat exchanger 14. The coolant flows between compressor12 and heat exchanger 14 from an outlet of compressor 12 toward an inletof heat exchanger 14 via coolant passage 21. Coolant passages 22 to 24each are a passage for causing the coolant to flow from heat exchanger14 to expansion valve 16. The coolant flows between heat exchanger 14and expansion valve 16 from an outlet of heat exchanger 14 toward aninlet of expansion valve 16 via coolant passages 22 to 24.

Coolant passage 25 is a passage for causing the coolant to flow fromexpansion valve 16 to heat exchanger 18. The coolant flows betweenexpansion valve 16 and heat exchanger 18 from an outlet of expansionvalve 16 to the inlet of heat exchanger 18 via coolant passage 25.Coolant passages 26 and 27 each are a passage for causing the coolant toflow from heat exchanger 18 to compressor 12. The coolant flows betweenheat exchanger 18 and compressor 12 from the outlet of heat exchanger 18to an inlet of compressor 12 via coolant passages 26 and 27.

Vapor compression refrigeration cycle 10 is configured by compressor 12,heat exchangers 14 and 15, expansion valve 16, and heat exchanger 18coupled via coolant passages 21 to 27. In addition, the coolant used forvapor compression refrigeration cycle 10 may be carbon dioxide,hydrocarbon such as propane and isobutane, ammonia, fluorocarbons, wateror the like, for example.

The route through which the coolant flows from the outlet of heatexchanger 14 toward the inlet of expansion valve 16 includes a coolantpassage 22 extending from the outlet side of heat exchanger 14 to a flowrate regulating valve 28 described later, a coolant passage 23 coupledto the inlet side of heat exchanger 15, and a coolant passage 24 throughwhich the coolant flows from the outlet side of heat exchanger 15 toexpansion valve 16.

The route of the coolant flowing between heat exchanger 14 and heatexchangers 15 further includes a coolant passage 33 branching fromcoolant passage 22 and extending to an electronic expansion valve 38described later, a coolant passage 34 allowing communication betweenelectronic expansion valve 38 and cooling unit 30, a coolant passage 35allowing communication between cooling unit 30 and a switching valve 52described later, and a coolant passage 36 allowing communication betweenswitching valve 52 and coolant passage 23. The coolant liquid flows fromheat exchanger 14 through coolant passages 33 and 34 into cooling unit30. The coolant having passed through cooling unit 30 flows throughcoolant passages 35 and 36, and back to coolant passage 23. Cooling unit30 is provided on the route of the coolant that flows from heatexchanger 14 toward heat exchanger 15.

Cooling device 1 includes a coolant route arranged in parallel withcoolant passages 22 and 23 between heat exchangers 14 and 15, andcooling unit 30 is disposed on this coolant route. Cooling unit 30 isprovided on one of a plurality of passages connected in parallel in theroute of the coolant flowing between heat exchanger 14 and heatexchanger 15. Cooling unit 30 includes HV (Hybrid Vehicle) equipment 31that is electrical equipment mounted in a vehicle, and a cooling passage32 serving as a pipe line through which the coolant flows. HV equipment31 is an example of a heat source. Cooling passage 32 has one endconnected to coolant passage 34, and the other end connected to coolantpassage 35.

The coolant route connected in parallel with coolant passages 22 and 23includes coolant passages 33 and 34 on the upstream side of cooling unit30 (on the side close to heat exchanger 14), cooling passage 32 includedin cooling unit 30, and coolant passages 35 and 36 on the downstreamside of cooling unit 30 (on the side close to heat exchanger 15).Coolant passages 33 and 34 each are a passage branching from coolantpassage 22 and through which the liquid-phase coolant flows from heatexchanger 14 to cooling unit 30. Coolant passages 35 and 36 each are apassage through which the coolant is returned from cooling unit 30 tocoolant passage 23 and flows to heat exchanger 15.

The coolant liquid flowing out of heat exchanger 14 flows throughcoolant passages 22, 33 and 34 toward cooling unit 30. The coolantflowing to cooling unit 30 and flowing through cooling passage 32absorbs heat from HV equipment 31 as a heat source, to cool HV equipment31. Cooling unit 30 cools HV equipment 31 using the liquid-phase coolantthat is condensed in heat exchanger 14 and flows through cooling passage32. In cooling unit 30, heat exchange is performed between the coolantflowing through cooling passage 32 and HV equipment 31, thereby coolingHV equipment 31 and heating the coolant. The coolant further flows fromcooling unit 30 through coolant passages 35 and 36 and reaches heatexchanger 15 through coolant passage 23.

Cooling unit 30 is provided so as to have a structure that allows heatexchange between HV equipment 31 and the coolant to be performed incooling passage 32. In the present embodiment, cooling unit 30 includesa cooling passage 32 that is, for example, formed to have an outerperipheral surface coming in direct contact with the housing of HVequipment 31. Cooling passage 32 has a portion that is adjacent to thehousing of HV equipment 31. In this portion, it becomes possible toperform heat exchange between the coolant flowing through coolingpassage 32 and HV equipment 31.

HV equipment 31 is directly connected to an outer peripheral surface ofcooling passage 32 forming a part of the coolant route extending fromheat exchanger 14 to head exchanger 15 in vapor compressionrefrigeration cycle 10. Thus, HV equipment 31 is cooled. Since HVequipment 31 is arranged on the outside of cooling passage 32, HVequipment 31 does not interfere with the flow of the coolant flowingthrough cooling passage 32. Therefore, since the pressure loss of vaporcompression refrigeration cycle 10 does not increase, HV equipment 31can be cooled without increasing the motive power of compressor 12.

Alternatively, cooling unit 30 may include an optional known heat pipearranged between HV equipment 31 and cooling passage 32. In this case,HV equipment 31 is connected to the outer peripheral surface of coolingpassage 32 via the heat pipe. This HV equipment 31 is cooled by heattransfer from HV equipment 31 through the heat pipe to cooling passage32. HV equipment 31 is used as a heating unit of the heat pipe andcooling passage 32 is used as a cooling unit of the heat pipe, therebyraising the heat transfer efficiency between cooling passage 32 and HVequipment 31. Consequently, the cooling efficiency for HV equipment 31can be improved. For example, a wick-type heat pipe can be used.

Since the heat pipe can reliably transfer heat from HV equipment 31 tocooling passage 32, HV equipment 31 and cooling passage 32 may be spacedapart from each other, and cooling passage 32 does not have to bearranged in a complicated manner for bringing cooling passage 32 intocontact with HV equipment 31. Consequently, the degree of freedom inarrangement of HV equipment 31 can be improved.

HV equipment 31 includes electric equipment generating heat by supplyand reception of electric power. The electric equipment includes, forexample, at least any one of an inverter for converting direct-current(DC) power to alternate-current (AC) power, a motor generator as arotating electric machine, a battery as a power storage device, a boostconverter for boosting the voltage of the battery, a DC/DC converter forstepping down the voltage of the battery, and the like. The battery is asecondary battery such as a lithium ion battery or a nickel-metalhydride battery. In place of the battery, a capacitor may be employed.

The coolant passes through a coolant circulating flow passage includingcompressor 12, heat exchangers 14 and 15, expansion valve 16, and heatexchanger 18 sequentially connected by coolant passages 21 to 27, andcirculates through vapor compression refrigeration cycle 10. The coolantflows through vapor compression refrigeration cycle 10 so as tosequentially pass through the points A, B, C, D, E, and F shown inFIG. 1. Thus, the coolant circulates through compressor 12, heatexchangers 14 and 15, expansion valve 16, and heat exchanger 18.

FIG. 2 is a Monier chart showing the state of the coolant in vaporcompression refrigeration cycle 10. In FIG. 2, the horizontal axisdenotes a specific enthalpy of the coolant while the vertical axisdenotes an absolute pressure of the coolant. The unit of the specificenthalpy is kJ/kg and the unit of the absolute pressure is MPa. Thecurve shown in the figure is a saturated vapor line and a saturatedliquid line of the coolant.

FIG. 2 represents a thermal dynamic state of the coolant at each point(that is, points A, B, C, D, E and F) in vapor compression refrigerationcycle 10 that flows from coolant passage 22 at the outlet of heatexchanger 14 into cooing unit 30 via coolant passages 33 and 34, coolsHV equipment 31, and returns from cooling unit 30 through coolantpassages 35 and 36 to coolant passage 23 at the inlet of heat exchanger15.

As shown in FIG. 2, the coolant in the superheated vapor state takeninto compressor 12 (point A) is adiabatically compressed along anisentropic line in compressor 12. As the compression progresses, thecoolant rises in pressure and temperature, and turns intohigh-temperature and high-pressure superheated vapor with a high degreeof superheat (point B). The area of the region shaded by dashed-twodotted lines in FIG. 2 shows the motive power of compressor 12 requiredfor adiabatically compressing the coolant from point A to point B.

The high-temperature and high-pressure coolant in the superheated vaporstate that has been adiabatically compressed in compressor 12 flows intoheat exchanger 14, where this coolant is cooled. The gas-phase coolantdischarged from compressor 12 radiates heat into the ambient environmentin heat exchanger 14, thereby being cooled and then condensed(liquefied). By heat exchange with the outside air in heat exchanger 14,the coolant is lowered in temperature and liquefied. The high-pressurecoolant vapor having entered into heat exchanger 14 turns into drysaturated vapor from superheated vapor while maintaining equal pressurein heat exchanger 14, radiates latent heat of condensation and isgradually liquefied, and turns into moist vapor in the gas-liquid mixedstate. Then, all the coolant condenses into saturated liquid (point C).

The coolant in the saturated liquid state flowing out of heat exchanger14 flows through coolant passages 22, 33 and 34 into cooling passage 32of cooling unit 30, to cool HV equipment 31. In cooling unit 30, heat isradiated into the liquid coolant that has passed through heat exchanger14 and turned into a condensed saturated liquid state, thereby coolingHV equipment 31. By heat exchange with HV equipment 31, the coolant isheated to increase the dryness of the coolant. The coolant receiveslatent heat from HV equipment 31 and partially evaporates, therebyturning into moist vapor in a gas-liquid two-phase state formed of amixture of saturated liquid and saturated vapor (point D).

Then, the coolant flows into heat exchanger 15 through coolant passages35, 36 and 23. The moist vapor of the coolant is cooled by heat exchangewith outside air in heat exchanger 15 and thereby again condensed. Whenall the coolant is condensed, it turns into saturated liquid, and turnsinto supercooled liquid (point E) which has been supercooled byradiating sensible heat. Then, the coolant flows into expansion valve 16through coolant passage 24. At expansion valve 16, the coolant in thesupercooled liquid state is subjected to throttle expansion, and thetemperature and pressure are lowered without a change in a specificenthalpy, so that low-temperature and low-pressure moist vapor in thegas-liquid mixed state is obtained (point F).

The coolant in the moist vapor state flowing out of expansion valve 16flows into heat exchanger 18 through coolant passage 25. The coolant inthe moist vapor state flows into the tube of heat exchanger 18. Whenflowing through the tube of heat exchanger 18, the coolant absorbs heatof the air-conditioning air as latent heat of evaporation via the fin,thereby being evaporated while maintaining the equal pressure. Heatexchanger 18 is disposed within a duct through which theair-conditioning air flows, and performs heat exchange between thecoolant and the air-conditioning air to adjust the temperature of theair-conditioning air. The air-conditioning air may be outside air, ormay be air within the vehicle cabin. During the cooling operation, theair-conditioning air is cooled in heat exchanger 18, and the coolant isheated by heat transferred from the air-conditioning air.

When all the coolant turns into dry saturated vapor, the coolant vaporis further raised in temperature by sensible heat and turns intosuperheated vapor (point A). After that, the coolant is sucked intocompressor 12 through coolant passages 26 and 27. Compressor 12compresses the coolant flowing from heat exchanger 18.

In accordance with such a cycle, the coolant continuously repeats thestate changes of compression, condensation, throttle expansion, andevaporation. In the description of the vapor compression refrigerationcycle set forth above, the theoretical refrigeration cycle is described.However, in actual vapor compression refrigeration cycle 10, loss incompressor 12, and pressure loss and heat loss in the coolant should betaken into consideration.

During the operation of vapor compression refrigeration cycle 10, thecoolant absorbs heat of evaporation from the air in the vehicle cabinwhen it evaporates in heat exchanger 18 acting as an evaporator.Thereby, this coolant cools the vehicle cabin. In addition, thehigh-pressure liquid coolant, which has flowed out of heat exchanger 14,flows into cooling unit 30 and subjected to heat exchange with HVequipment 31, thereby cooling HV equipment 31. Utilizing vaporcompression refrigeration cycle 10 for air conditioning in the vehiclecabin, cooling device 1 cools HV equipment 31 serving as a heat sourcemounted in the vehicle. It is desirable that the temperature requiredfor cooling HV equipment 31 is at least lower than the upper limit valueof the target temperature range as a temperature range of HV equipment31.

Since HV equipment 31 is cooled utilizing vapor compressionrefrigeration cycle 10 provided for cooling a portion to be cooled inheat exchanger 18, there is no need to provide devices such as adedicated water circulating pump or cooling fan for cooling HV equipment31. Accordingly, since the configuration required for cooling device 1of HV equipment 31 can be reduced and the device configuration can besimplified, the production cost for cooling device 1 can be reduced. Inaddition, since there is no need to operate a power source such as apump and a cooling fan for cooling HV equipment 31, the powerconsumption for operating the power source is not required. Therefore,the power consumption for cooling HV equipment 31 can be reduced.

In heat exchanger 14, the coolant only has to be cooled to the state ofsaturated liquid. In this case, the coolant in the saturated liquidstate is supplied to cooling unit 30. The coolant in the moist vaporstate that has received latent heat of evaporation from HV equipment 31and partially evaporated is cooled again in heat exchanger 15. The stateof the coolant is changed at a constant temperature until the coolant inthe moist vapor state is condensed and completely turned into saturatedliquid. Heat exchanger 15 further supercools the liquid-phase coolant tothe supercool degree required for cooling the vehicle cabin. Since thesupercool degree of the coolant does not need to be excessively raised,the volumes of heat exchangers 14 and 15 can be decreased. Therefore,the cooling ability for the vehicle cabin can be ensured, and heatexchangers 14 and 15 can be reduced in size, so that cooling device 1that is reduced in size and advantageous for vehicle installation can beachieved.

As a route through which the coolant flows from heat exchanger 14 towardexpansion valve 16, coolant passages 22 and 23 not extending throughcooling unit 30, and coolant passages 33, 34, 35, and 36 and coolingpassage 32 each serving as a route of the coolant flowing throughcooling unit 30 to cool HV equipment 31 are arranged in parallel. Thecooling system of HV equipment 31 including coolant passages 33 to 36 isconnected in parallel with coolant passages 22 and 23. Accordingly, onlya part of the coolant flowing out of heat exchanger 14 flows intocooling unit 30. The amount of the coolant required for cooling HVequipment 31 flows through cooling unit 30, and HV equipment 31 isappropriately cooled. Therefore, HV equipment 31 can be prevented frombeing supercooled.

The route of the coolant flowing from heat exchanger 14 into heatexchanger 15 without flowing through cooling unit 30 and the route ofthe coolant flowing from heat exchanger 14 through cooling unit 30 intoheat exchanger 15 are arranged in parallel, and only a part of thecoolant flows through coolant passages 33 to 36, thereby allowingreduction in pressure loss caused when the coolant flows through thecooling system of HV equipment 31. Since all the coolant does not flowinto cooling unit 30, it becomes possible to reduce the pressure lossassociated with the coolant flowing through cooling unit 30.Accordingly, it becomes possible to reduce the power consumptionrequired for operating compressor 12 for circulating the coolant.

When the low-temperature and low-pressure coolant having passed throughexpansion valve 16 is used for cooling HV equipment 31, the ability ofheat exchanger 18 to cool the air in the vehicle cabin is decreased,thereby lowering the ability to cool the vehicle cabin. In contrast,according to cooling device 1 in the present embodiment, in vaporcompression refrigeration cycle 10, the high-pressure coolant dischargedfrom compressor 12 is condensed by both of heat exchanger 14 as thefirst condenser and heat exchanger 15 as the second condenser. Two heatexchangers 14 and 15 are arranged between compressor 12 and expansionvalve 16. Cooling unit 30 cooling HV equipment 31 is disposed betweenheat exchanger 14 and heat exchanger 15. Heat exchanger 15 is disposedon the route of the coolant flowing from cooling unit 30 towardexpansion valve 16.

The coolant heated by latent heat of evaporation received from HVequipment 31 is sufficiently cooled in heat exchanger 15, so that thecoolant has a temperature and pressure at the outlet of expansion valve16 that are essentially required for cooling the vehicle cabin.Accordingly, since it becomes possible to sufficiently increase theamount of heat received from outside when the coolant evaporates in heatexchanger 18, the air-conditioning air passing through heat exchanger 18can be sufficiently cooled. In this way, by setting the heat radiationability of heat exchanger 15 allowing sufficient cooling of the coolant,HV equipment 31 can be cooled without exerting an influence upon theability to cool the air in the vehicle cabin. Therefore, both of thecooling ability for HV equipment 31 and the cooling ability for thevehicle cabin can be reliably ensured.

When cooling HV equipment 31, the coolant flowing from heat exchanger 14into cooling unit 30 receives heat from HV equipment 31 and is thenheated. When the coolant is heated in cooling unit 30 to a temperatureequal to or higher than the saturated vapor temperature and the totalamount of the coolant evaporates, the amount of heat exchange betweenthe coolant and HV equipment 31 is decreased, thereby preventingefficient cooling of HV equipment 31 and also increasing the pressureloss caused when the coolant flows through a pipe line. Accordingly, itis desirable to sufficiently cool the coolant in heat exchanger 14 tosuch an extent that the total amount of the coolant does not evaporateafter HV equipment 31 is cooled.

Specifically, the state of the coolant at the outlet of heat exchanger14 is brought closer to saturated liquid, and typically, the coolant isbrought into the state on the saturated liquid line at the outlet ofheat exchanger 14. As a result of allowing heat exchanger 14 to have anability to sufficiently cool the coolant, the heat radiating ability ofheat exchanger 14 to radiate heat from the coolant becomes higher thanthe heat radiating ability of heat exchanger 15. By sufficiently cooingthe coolant in heat exchanger 14 having a relatively greater heatradiating ability, the coolant having received heat from ITV equipment31 can be maintained in the state of moist vapor, so that the reductionin the amount of heat exchange between the coolant and HV equipment 31can be avoided. Therefore, HV equipment 31 can be cooled in a fullyefficient manner. The coolant in the moist vapor state that has cooledHV equipment 31 is efficiently cooled again in heat exchanger 15, andcooled to the state of supercooled liquid to an extent below thesaturated temperature. Therefore, cooling device 1 can be provided thatcan ensure both of the cooling ability for the vehicle cabin and thecooling ability for HV equipment 31.

Referring back to FIG. 1, cooling device 1 includes flow rate regulatingvalve 28. Flow rate regulating valve 28 is connected to coolant passages22 and 23 forming one passage not extending through cooling unit 30among the coolant passages connected in parallel and extending from heatexchanger 14 toward expansion valve 16. Flow rate regulating valve 28changes its valve opening degree to increase or decrease the pressureloss of the coolant flowing from coolant passage 22 through flow rateregulating valve 28 into coolant passage 23. Thereby, flow rateregulating valve 28 arbitrarily adjusts the flow rate of the coolantdirectly flowing from coolant passage 22 into coolant passage 23 and theflow rate of the coolant flowing through the cooling system of HVequipment 31 including cooling passage 32.

For example, when flow rate regulating valve 28 is fully closed to setits valve opening degree at 0%, the total amount of the coolant flowingout of heat exchanger 14 flows through coolant passages 33 and 34 intocooling unit 30. If the valve opening degree of flow rate regulatingvalve 28 is increased, the coolant flowing from heat exchanger 14 intocoolant passage 22 is to include a coolant increased in flow rate thatflows through coolant passages 22 and 23 directly into heat exchanger15, and a coolant decreased in flow rate that flows through coolantpassages 33 and 34 into cooling passage 32 to cool HV equipment 31. Ifthe valve opening degree of flow rate regulating valve 28 is decreased,the coolant flowing from heat exchanger 14 into coolant passage 22 is toinclude a coolant decreased in flow rate that flows through coolantpassages 22 and 23 directly into heat exchanger 15, and a coolantincreased in flow rate that flows through coolant passages 33 and 34 tocool HV equipment 31.

When the valve opening degree of flow rate regulating valve 28 isincreased, the flow rate of the coolant cooling HV equipment 31 isdecreased, thereby decreasing the cooling ability for HV equipment 31.When the valve opening degree of flow rate regulating valve 28 isdecreased, the flow rate of the coolant cooling HV equipment 31 isincreased, thereby improving the cooling ability for HV equipment 31.Since the amount of the coolant flowing through HV equipment 31 can beoptimally adjusted by using flow rate regulating valve 28, supercoolingof HV equipment 31 can be reliably prevented. In addition, both of thepressure loss associated with the coolant flowing through the coolingsystem of HV equipment 31 and the power consumption of compressor 12 forcirculating the coolant can be reliably decreased.

Cooling device 1 includes an electronic expansion valve 38 connected tocoolant passages 33 and 34 on the upstream side with respect to coolingunit 30. Electronic expansion valve 38 is provided in the route of thecoolant between heat exchanger 14 and cooling unit 30. Electronicexpansion valve 38 is provided such that the opening degree can beadjusted in an electrically-powered manner. Electronic expansion valve38 may be a valve whose valve opening degree is changed in accordancewith the rotation amount of a rotor disposed within the valve androtating in response to an instruction for the valve opening degree.Electronic expansion valve 38 is configured to minimize the pressureloss of the coolant flowing through electronic expansion valve 38 whenit is fully opened (the opening degree is 100%), and also to decreasethe temperature and the pressure of the coolant by subjecting thecoolant to throttle expansion by decreasing its opening degree.

When electronic expansion valve 38 is fully opened, the coolant flowingthrough coolant passage 33 and the coolant flowing through coolantpassage 34 are approximately equal in temperature and pressure. On theother hand, when the opening degree of electronic expansion valve 38 isdecreased, the coolant is subjected to throttle expansion in electronicexpansion valve 38. In this case, the specific enthalpy of the coolantdoes not change, but the temperature and the pressure are lowered.Accordingly, the coolant flowing through coolant passage 34 becomeslower in temperature and pressure than the coolant flowing throughcoolant passage 33. By arbitrarily adjusting the opening degree ofelectronic expansion valve 38, the temperature and the pressure of thecoolant supplied to cooling unit 30 through coolant passage 34 can beadjusted, so that the coolant under the optimal conditions for coolingHV equipment 31 can be supplied to cooling unit 30.

Cooling device 1 further includes a switching valve 52 switching thecommunication state between coolant passages 35 and 36. Switching valve52 is provided as a three-way valve having pipe connection ports atthree positions. Coolant passage 35 is connected to the first pipeconnection port of switching valve 52. Coolant passage 36 is connectedto the second pipe connection port of switching valve 52. A bypass route41 is connected to the third pipe connection port of switching valve 52.Bypass route 41 connects switching valve 52 and the route of the coolantextending between heat exchanger 18 and compressor 12. Typically, bypassroute 41 has one end connected to switching valve 52, and the other endconnected to gas-liquid separator 40 disposed between heat exchanger 18and compressor 12.

Switching valve 52 is switched to be opened or closed, thereby switchingbetween the flow of the coolant flowing from coolant passage 35 towardcoolant passage 36 and the flow of the coolant flowing from coolantpassage 35 toward bypass route 41. Switching valve 52 has a function asa route selection unit that selectively switches between the flow of thecoolant flowing from cooling unit 30 through heat exchanger 15 towardexpansion valve 16 and the flow of the coolant flowing out of coolingunit 30 through bypass route 41 into gas-liquid separator 40. Byswitching the coolant route using switching valve 52, the coolant havingcooled HV equipment 31 can be caused to flow through the routearbitrarily selected from a route extending through coolant passages 36and 23 to heat exchanger 15 and a route extending through bypass route41 to gas-liquid separator 40 on the upstream side of compressor 12.

FIG. 1 shows the case where the air conditioner for cooling the vehiclecabin is being operated and also the case where normal cooling for HVequipment 31 is required. In this case, compressor 12 is in the operatedstate in order to circulate the coolant through the entire vaporcompression refrigeration cycle 10. The valve opening degree of flowrate regulating valve 28 is adjusted such that a sufficient coolant forcooling HV equipment 31 flow into cooling unit 30. Electronic expansionvalve 38 is fully opened. Switching valve 52 is switched to be openedand closed so as to allow communication between coolant passage 35 andcoolant passage 36, and to disallow bypass route 41 to be incommunication with both of coolant passages 35 and 36. Switching valve52 is operated so as to cause the coolant to flow from cooling unit 30through heat exchanger 15 to expansion valve 16, and the coolant routeis selected such that the coolant flows through the entire coolingdevice 1. The coolant is circulated through vapor compressionrefrigeration cycle 10.

Then, the low-temperature and low-pressure coolant that has been turnedinto mist by expansion valve 16 is supplied to heat exchanger 18,thereby allowing cooling of the air-conditioning air. Accordingly, theability to cool the vehicle cabin can be ensured. In addition, sinceheat is taken from HV equipment 31 by the latent heat of evaporation ofthe coolant flowing from heat exchanger 14 into cooling unit 30, HVequipment 31 can be efficiently cooled.

FIG. 3 is a schematic diagram showing cooling device 1 in the case wherethe required cooling performance for HV equipment 31 is raised. FIG. 3shows the case where the air conditioner for cooling the vehicle cabinis being operated, and also the case where improvement in coolingperformance for HV equipment 31 is required because the heat amountgenerated from HV equipment 31 is increased, such as the case where thedriver operating the vehicle selects a sport driving mode and HVequipment 31 is operated in a highly loaded state, for example. In thiscase, as in the state shown in FIG. 1, compressor 12 is in an operatedstate and the opening degree of flow rate regulating valve 28 isadjusted. On the other hand, electronic expansion valve 38 is narrowedsuch that its opening degree is decreased. Switching valve 52 isswitched to be opened or closed so as to allow communication betweencoolant passage 35 and bypass route 41, and to disallow coolant passage36 to be in communication with both of coolant passage 35 and bypassroute 41.

In this case, the coolant flowing through cooling unit 30 and used forcooling HV equipment 31 flows through switching valve 52 into bypassroute 41, and flows into gas-liquid separator 40 on the upstream side ofcompressor 12. Bypass route 41 is directly connected to switching valve52 and gas-liquid separator 40. The coolant for cooling HV equipment 31flows through the route extending from cooling unit 30 throughgas-liquid separator 40 into compressor 12, but does not flow into heatexchanger 15, expansion valve 16 and heat exchanger 18. Bypass route 41is provided as a coolant route that bypasses heat exchanger 15,expansion valve 16 and heat exchanger 18.

In this case, the sport driving mode is a vehicle driving mode aiming attemporarily improving the vehicle running performance. In the case of ahybrid vehicle, control is performed to supply a large current to adrive motor, to temporarily boost the voltage supplied to the drivemotor, thereby allowing improvement in the output from the drive motor.For example, the vehicle running performance can be improved bytemporarily applying a high voltage of 650V to the motor rated at 500V.

By setting the vehicle in the sport driving mode, the vehicle runningperformance can be improved without changing the specifications of HVequipment 31 and at no additional cost. The user who operates thevehicle can feel the driving operation in the mode prioritizing vehiclerunning, while driving the same vehicle, by a simple operation ofswitching the driving mode. Meanwhile, in order to apply a high voltageequal to or higher than the rating voltage to the motor, HV equipment 31is to be operated in the overloaded state, with the result that theamount of generated heat from HV equipment 31 is increased as comparedwith that in the normal driving mode. Accordingly, in the sport drivingmode, it is necessary to maintain the temperature of HV equipment 31within an acceptable range to avoid overheating of HV equipment 31.Therefore, the ability to cool HV equipment 31 needs to be improved.

FIG. 4 is a schematic diagram showing cooling device 1 in the case wherethe required cooling performance for HV equipment 31 is raised while anair conditioner is stopped. FIG. 4 shows the case where an airconditioner is being stopped and the case where improvement in coolingperformance for HV equipment 31 is required because the heat amountgenerated from HV equipment 31 is increased. In this case, flow rateregulating valve 28 is fully closed (the opening degree is 0%).Electronic expansion valve 38 is narrowed such that its opening degreeis decreased. Switching valve 52 is switched to be opened or closed soas to allow communication between coolant passage 35 and bypass route41, and disallow coolant passage 36 to be in communication with both ofcoolant passage 35 and bypass route 41.

Compressor 12 is set in the operated state in order to provide drivingforce for allowing the coolant flowing through bypass route 41 tocirculate through the refrigeration cycle. Compressor 12 is forciblystarted while the air conditioner is stopped, thereby producing a flowof the coolant flowing through a circulation route including coolingunit 30 to cool HV equipment 31. The coolant flowing through coolingunit 30 flows through switching valve 52 into bypass route 41, andfurther into gas-liquid separator 40.

FIG. 5 is a Mollier chart showing the state of the coolant in the casewhere the required cooling performance for HV equipment 31 is raised. InFIG. 5, the horizontal axis denotes a specific enthalpy of the coolantwhile the vertical axis denotes an absolute pressure of the coolant. Theunit of the specific enthalpy is kJ/kg and the unit of the absolutepressure is MPa. The curve shown in the figure is a saturated vapor lineand a saturated liquid line of the coolant.

As shown in FIGS. 3 and 4, for improving the required coolingperformance for HV equipment 31, a coolant circulation route is formedthat extends sequentially through compressor 12, heat exchanger 14,electronic expansion valve 38, and cooling unit 30. The coolant used forcooling HV equipment 31 circulates through this coolant circulationroute. The coolant flows through vapor compression refrigeration cycle10 so as to sequentially pass through points A, B, C, and G shown inFIG. 3. Thus, the coolant circulates through compressor 12, heatexchanger 14, electronic expansion valve 38, and cooling unit 30. FIG. 5represents a thermal dynamic state of the coolant at each point (thatis, points A, B, C, and G) in vapor compression refrigeration cycle 10that flows from coolant passage 22 at the outlet of heat exchanger 14into cooling unit 30 via coolant passages 33 and 34, cools HV equipment31, and returns from cooling unit 30 through coolant passage 35 andbypass route 41 to the upstream side of compressor 12.

As shown in FIG. 5, the coolant in the superheated vapor state takeninto compressor 12 (point A) is adiabatically compressed along anisentropic line in compressor 12. As the compression progresses, thecoolant rises in pressure and temperature, and turns intohigh-temperature and high-pressure superheated vapor with a high degreeof superheat (point B). The area of the region shaded by dashed-twodotted lines in FIG. 5 shows the motive power of compressor 12 requiredfor adiabatically compressing the coolant from point A to point B.

The high-temperature and high-pressure coolant in the superheated vaporstate that has been adiabatically compressed in compressor 12 flows intoheat exchanger 14, where this coolant is cooled. The gas-phase coolantdischarged from compressor 12 radiates heat into the ambient environmentin heat exchanger 14, thereby being cooled and then condensed(liquefied). By heat exchange with the outside air in heat exchanger 14,the coolant is lowered in temperature and liquefied. The high-pressurecoolant vapor having entered into heat exchanger 14 turns into drysaturated vapor from superheated vapor while maintaining equal pressurein heat exchanger 14, radiates latent heat of condensation and isgradually liquefied, and then, turns into moist vapor in the gas-liquidmixed state. Then, all the coolant condenses into saturated liquid(point C).

The coolant in the saturate liquid state flowing out of heat exchanger14 flows into electronic expansion valve 38 through coolant passages 22and 33. At electronic expansion valve 38, the coolant is subjected tothrottle expansion, lowered in temperature and pressure without changingthe specific enthalpy, and turns into moist vapor in the gas-liquidmixed state (point G). Electronic expansion valve 38 has a function as atemperature lowering unit for lowering the temperature of the coolant onthe upstream side of cooling unit 30, and lowering the temperature ofthe coolant supplied to cooling unit 30.

The coolant in the moist vapor state that has been subjected to throttleexpansion by electronic expansion valve 38 flows through coolant passage34 into cooling passage 32 of cooling unit 30, thereby cooling HVequipment 31. In cooling unit 30, heat is radiated to the coolant thathas passed through electronic expansion valve 38 and has been decreasedin temperature and pressure, thereby cooling HV equipment 31. By heatexchange with HV equipment 31, the coolant is heated to increase thedryness of the coolant. The coolant absorbs heat of HV equipment 31 aslatent heat of evaporation and thereby evaporates while maintaining theequal pressure. When all the coolant turns into dry saturated vapor, thecoolant vapor is further increased in temperature by sensible heat andturns into superheated vapor (point A).

After that, the coolant is sucked into compressor 12 through bypassroute 41, gas-liquid separator 40 and coolant passage 27. Compressor 12compresses the coolant flowing from coolant passage 27. In accordancewith such a cycle, the coolant continuously repeats the state changes ofcompression, condensation, throttle expansion, and evaporation.

As described above, cooling device 1 according to the present embodimentincludes bypass route 41 bypassing heat exchanger 15, expansion valve 16and heat exchanger 18, and switching valve 52 selectively switching thecoolant flow. When normal cooling of HV equipment 31 is required,switching valve 52 selects the flow of the coolant flowing throughcoolant passage 36, to form a flow of the coolant flowing from coolingunit 30 into heat exchanger 15. When the amount of heat generated by HVequipment 31 is increased, switching valve 52 switches the coolant flowto select the flow of the coolant flowing through bypass route 41,thereby forming a flow of the coolant flowing from cooling unit 30through bypass route 41 into gas-liquid separator 40.

Accordingly, heat is transferred from HV equipment 31 to the coolantuntil the coolant condensed and liquefied in heat exchanger 14 turnsinto superheated vapor, so that HV equipment 31 can be cooled. Since theamount of heat exchange between the coolant and HV equipment 31 incooling unit 30 can be increased, the ability to cool HV equipment 31 isenhanced. Since the ability to cool HV equipment 31 can be enhanced inaccordance with an increase in the amount of heat generated from HVequipment 31, cooling performance suitable for the amount of heatgenerated from HV equipment 31 can be achieved.

Furthermore, electronic expansion valve 38 is provided on the upstreamside of cooling unit 30. When the amount of heat generated by HVequipment 31 is increased, the opening degree of this electronicexpansion valve 38 is adjusted to subject the coolant to throttleexpansion, thereby turning the coolant into a low-temperature andlow-pressure mist-like coolant, and lowering the temperature of thecoolant flowing through cooling unit 30. By supplying a low-temperaturecoolant to cooling unit 30, the heat transfer efficiency from HVequipment 31 to the coolant can be improved, so that the amount of heatabsorbed by the coolant as latent heat of evaporation from HV equipment31 can be increased. When the low-temperature coolant is evaporated bythe heat of HV equipment 31, the amount of heat exchange between thecoolant and HV equipment 31 can be increased. Accordingly, the abilityto cool HV equipment 31 can be further improved.

When improvement in the ability to cool HV equipment 31 is required inaccordance with the cooling performance required for HV equipment 31,compressor 12 and electronic expansion valve 38 are controlled to lowerthe temperature of the coolant flowing through cooling unit 30, with theresult that the temperature of the coolant supplied to cooling unit 30can be optimally set. The equipment for lowering the temperature of thecoolant may be any equipment, and for example, another heat exchanger, aPeltier devices or the like may be disposed on the upstream side ofcooling unit 30. In the case of the configuration as described above inwhich the coolant is subjected to throttle expansion by electronicexpansion valve 38 to lower the temperature of the coolant, the devicestructure can be simplified while the temperature of the coolant can belowered without using additional motive power.

When comparing the motive power of compressor 12 shown in FIG. 2 and themotive power of compressor 12 shown in FIG. 5 each of which arerepresented by shading of dashed-two dotted lines, the motive power ofcompressor 12 shown in FIG. 5 is relatively small. For example, in thecase where the opening degree of electronic expansion valve 38 is setsuch that the coolant of about 60° C. at the outlet of heat exchanger 14is cooled to a temperature that is lower by 5° C. than the outside-airtemperature (for example, 25° C. when the outside-air temperature is 30°C.), the motive power of compressor 12 is reduced to approximately halfof the motive power required during the operation of the air conditionershown in FIG. 1. In order to achieve the coolant temperature suitablefor the cooling performance required for HV equipment 31, a part or allof the coolant is caused to flow through bypass route 41, therebyallowing control for decreasing the motive power of compressor 12.

Bypass route 41 is coupled to gas-liquid separator 40, and the coolantflowing from cooling unit 30 through bypass route 41 flows intogas-liquid separator 40. Gas-liquid separator 40 separates the coolantinto a gas-phase coolant and a liquid-phase coolant. Gas-liquidseparator 40 stores coolant liquid that is a liquid-phase coolant andcoolant vapor that is a gas-phase coolant. The coolant liquid in thesaturated liquid state is stored in gas-liquid separator 40. The coolantliquid separated into a gas-phase coolant and a liquid-phase coolant ingas-liquid separator 40 is stored in gas-liquid separator 40. Gas-liquidseparator 40 functions as a liquid storage container temporarily storingthe coolant liquid in a liquid-state coolant.

When the coolant circulates not through heat exchangers 15 and 18 butonly through heat exchanger 14, a refrigeration cycle employing onlyheat exchanger 14 is applied. Accordingly, the amount of the coolantrequired for cooling HV equipment 31 is reduced. Gas-liquid separator 40is provided and a part of the coolant is stored in gas-liquid separator40, thereby allowing adjustment of the coolant amount within the cycle.Accordingly, the amount of the coolant circulating through therefrigeration cycle can be optimized. Thus, it becomes possible tosuppress occurrence of a defect that the coolant amount within therefrigeration cycle is excessively increased to raise the pressure.

A prescribed amount of the coolant liquid is stored in gas-liquidseparator 40, so that the flow rate of the coolant supplied to coolingunit 30 can be maintained also during load change. Gas-liquid separator40 has a liquid reservoir function, serves as a buffer against loadchange and can absorb this load change. Therefore, the coolingperformance for HV equipment 31 can be stabilized.

When the amount of heat exchange between the coolant and HV equipment 31in cooling unit 30 is relatively small and the amount of heat receivedby the coolant from HV equipment 31 is relatively small, heating of thecoolant in cooling unit 30 is suppressed. Accordingly, the coolant thathas been subjected to heat exchange with HV equipment 31 in cooling unit30 and flows through bypass route 41 into gas-liquid separator 40 may bein the state of moist vapor in the gas-liquid two-phase state wheresaturated liquid and saturated vapor are mixed. In this case, thecoolant is separated into a gas phase and a liquid phase withingas-liquid separator 40. The coolant in the gas-liquid two-phase statethat flows into gas-liquid separator 40 is separated into coolant liquidin the liquid state and coolant vapor in the gaseous state withingas-liquid separator 40.

Within gas-liquid separator 40, the coolant liquid accumulates in thelower portion while the coolant vapor accumulates in the upper portion.Coolant passage 27 has an end through which the coolant vapor flows outof gas-liquid separator 40. This end is coupled to the ceiling part ofgas-liquid separator 40, Only the coolant vapor is caused to flow fromthe ceiling side of gas-liquid separator 40 through coolant passage 27to the outside of gas-liquid separator 40. Thereby, only the gas-phasecoolant that has been reliably separated into a gas-phase coolant and aliquid-phase coolant by gas-liquid separator 40 can be supplied tocompressor 12. Consequently, the coolant liquid can be prevented fromflowing into compressor 12, so that it becomes possible to preventoccurrence of defects caused in compressor 12 by inclusion of a liquidcomponent into compressor 12.

As switching valve 52 switching the communication state between bypassroute 41 and each of coolant passages 35 and 36, a three-way valve maybe disposed at the branch between bypass route 41 and each of coolantpassages 35 and 36, as described above. Alternatively, a valve capableof opening and closing the coolant route may be provided at each ofcoolant passages 35 and 36 and bypass route 41, so that switching valve52 may be formed by these plurality of open-close valves. In each case,HV equipment 31 can be efficiently cooled during both of operation anddiscontinuation of vapor compression refrigeration cycle 10. It isconsidered that the space required for arranging the three-way valve maybe smaller than the space required for arranging a plurality ofopen-close valves. Thus, by using such a three-way valve, cooling device1 can be provided that is further reduced in size and excellent invehicle mountability. On the other hand, the open-close valve can beinexpensive since this valve only has to have a simple structureallowing the coolant passage to be opened and closed. By using aplurality of open-close valves, a relatively low-cost cooling device 1can be provided.

In the setting shown in FIG. 1, all the coolant flows into heatexchanger 18. In contrast, in the setting show in each of FIGS. 3 and 4,since a part of the coolant flows so as to bypass heat exchanger 18, theflow rate of the coolant flowing into heat exchanger 18 is decreased. Inother words, when the ability to cool HV equipment 31 needs to beimproved, for example, such as when the sport driving mode is selected,the ability to cool the vehicle cabin may deteriorate. In this case, theinfluence upon the cooling ability can be alleviated by adjusting theflow rate of the coolant by controlling the opening degree of flow rateregulating valve 28 so as to implement both of the cooling ability forHV equipment 31 and the air-conditioning cooling ability. Afterrecognizing the influence upon the air-conditioning cooling ability inthe state where the vehicle running performance is prioritized, thedriver is to select a sport driving mode.

In the above-described embodiment, an explanation has been given withregard to an example in which HV equipment 31 serving as a heat sourceis cooled by cooling device 1. In the case where the device to be cooledby cooling device 1 is for example a battery, when the temperature istoo low, the chemical change within the battery may be suppressed tocause a decrease in the output power density. Accordingly, moderatewarming is required. In cooling device 1 according to the presentembodiment, when heat exchange between the coolant and the outside airin heat exchanger 14 is suppressed by reducing the air volume ofcondenser fan 42, cooling of the coolant in heat exchanger 14 can besuppressed, so that the coolant flowing into cooling unit 30 can bemaintained at a relatively higher temperature. In this case, control canbe performed such that the coolant is condensed in heat exchanger 14 andcooling unit 30, and the battery can be warmed in cooling unit 30 byreceiving heat from the coolant. On the other hand, when it is desiredto rapidly cool the battery, electronic expansion valve 38 is narrowedto lower the temperature of the coolant supplied to cooling unit 30,thereby allowing improvement in the ability to cool the battery.

For example, assume that the equipment to be cooled by cooling device 1is a capacitor. When the temperature of the capacitor is relatively low,condensation of the coolant in heat exchanger 14 is suppressed, therebyrelatively increasing the specific enthalpy of the coolant flowing intocooling unit 30, so that the capacitor can be warmed. The capacitorrepeats charging/discharging momentarily. In this case, however, sincethe capacitor can be cooled by the low-temperature coolant that has beenturned into a mist state by throttle expansion in electronic expansionvalve 38, the cooling performance for the capacitor is improved.Therefore, since the number of cells in the capacitor can be reduced,significant cost reduction for the device can be achieved.

Second Embodiment

FIG. 6 is a schematic diagram showing the configuration of coolingdevice 1 according to the second embodiment. Switching valve 52 in thefirst embodiment is provided as a three-way valve, whereas switchingvalve 52 in the second embodiment is a four-way valve. Switching valve52 is provided as a four-way valve having pipe connection ports at fourpositions. Coolant passage 35 is connected to the first pipe connectionport of switching valve 52. Coolant passage 36 is connected to thesecond pipe connection port of switching valve 52. Bypass route 41 isconnected to the third pipe connection port of switching valve 52.Communication passage 51 is connected to the fourth pipe connection portof switching valve 52.

Communication passage 51 allows communication between coolant passage 21through which the coolant flows between compressor 12 and heat exchanger14, and coolant passage 35 forming a route of the coolant flowing fromcooling unit 30 toward expansion valve 16. Switching valve 52 isswitched to be opened or closed, thereby switching among the flow of thecoolant flowing from coolant passage 35 toward coolant passage 36, theflow of the coolant flowing from coolant passage 35 toward bypass route41 and the flow of the coolant flowing from coolant passage 35 towardcommunication passage 51. Switching valve 52 is provided such that theflow of the coolant flowing from cooling unit 30 toward communicationpassage 51 can be formed. Switching valve 52 is switched to be opened orclosed, thereby allowing or disallowing flow of the coolant throughcommunication passage 51.

By using switching valve 52 to switch the route of the coolant, thecoolant having cooled HV equipment 31 can be caused to flow through theroute arbitrarily selected from a route extending through coolantpassages 36 and 23 to heat exchanger 15, a route extending throughbypass route 41 to gas-liquid separator 40 on the upstream side ofcompressor 12, or a route extending through communication passage 51 andcoolant passage 21 to heat exchanger 14. A four-way valve is used asswitching valve 52, and the setting for opening/closing switching valve52 is changed, thereby implementing the configuration that allows flowof the coolant through communication passage 51. Since this allowssimplification of the device configuration, addition of devices can besuppressed and an increase in cost can be avoided.

FIG. 7 is a diagram showing settings of compressor 12 and valves foreach operation mode of cooling device 1. FIG. 7 shows the operationstate of compressor 12, the setting of the opening degree of each offlow rate regulating valve 28, electronic expansion valve 38 andswitching valve 52 in each operation mode in the case where coolingdevice 1 is operated in four different operation modes.

The “air-conditioner operation mode” of the operation modes shown inFIG. 7 is an operation mode in which the air conditioner for cooling thevehicle cabin is being operated, and normal cooling for HV equipment 31is required. In this case, the coolant needs to flow through the entirevapor compression refrigeration cycle 10 including expansion valve 16and heat exchanger 18 for the purpose of cooling the vehicle cabin.Accordingly, compressor 12 is in the operated state. The valve openingdegree of flow rate regulating valve 28 is adjusted such that sufficientcoolant for cooling HV equipment 31 flows into cooling unit 30.Electronic expansion valve 38 is fully opened.

Switching valve 52 is switched to be opened or closed so as to allowcommunication between coolant passage 35 and coolant passage 36, and todisallow bypass route 41 and communication passage 51 to be incommunication with both of coolant passages 35 and 36. Switching valve52 is operated such that the coolant is caused to flow from cooling unit30 through heat exchanger 15 into expansion valve 16, to select thecoolant route such that the coolant flows through the entire coolingdevice 1. Accordingly, the ability to cool the vehicle cabin using vaporcompression refrigeration cycle 10 can be ensured while HV equipment 31can be cooled efficiently.

It is to be noted that the operation state of cooling device 1 that hasbeen described with reference to FIG. 1 in the first embodimentcorresponds to this “air-conditioner operation mode”.

FIG. 8 is a schematic diagram showing cooling device 1 in the case wherevapor compression refrigeration cycle 10 is stopped. FIG. 9 is aschematic diagram showing the flow of the coolant cooling HV equipment31 while vapor compression refrigeration cycle 10 is stopped. The “heatpipe operation mode” of the operation modes shown in FIG. 7 is anoperation mode in which the air conditioner for cooling the vehiclecabin is being stopped, and normal cooling for HV equipment 31 isrequired, as shown in FIGS. 8 and 9.

In this case, vapor compression refrigeration cycle 10 is stopped, andthe coolant does not need to flow through the entire vapor compressionrefrigeration cycle 10. Accordingly, compressor 12 is in the stoppedstate. Flow rate regulating valve 28 is fully closed. Electronicexpansion valve 38 is fully opened. Switching valve 52 is switched to beopened or closed so as to allow communication between coolant passage 35and communication passage 51, and to disallow coolant passage 36 andbypass route 41 to be in communication with both of coolant passage 35and communication passage 51. Switching valve 52 is operated such thatthe coolant is circulated from cooling unit 30 to heat exchanger 14. Thecoolant does not flow from coolant passage 35 into coolant passage 36and bypass route 41, but flows through communication passage 51.

Thereby, a closed looped route is formed that extends from heatexchanger 14 sequentially through coolant passages 22, 33, electronicexpansion valve 38 and coolant passage 34 to cooling unit 30, andfurther, sequentially through coolant passage 35, switching valve 52,communication passage 51 and coolant passage 21 back to heat exchanger14. Also, a looped route is formed through which the coolant havingcooled HV equipment 31 and flowing through coolant passage 35 flowsthrough communication passage 51 into heat exchanger 14, to cause thecoolant to circulate between cooling unit 30 and heat exchanger 14without flowing through compressor 12. Thus, the coolant route isselected such that the coolant is caused circulate through the loopedroute connecting cooling unit 30 and heat exchanger 14.

The coolant can be circulated through this looped route so as to flowbetween heat exchanger 14 and cooling unit 30 without operatingcompressor 12. When cooling HV equipment 31, the coolant evaporates withthe latent heat of evaporation received from HV equipment 31. Thecoolant vapor evaporated by heat exchange with HV equipment 31 flowsinto heat exchanger 14 sequentially through coolant passage 35,communication passage 51 and coolant passage 21. In heat exchanger 14,the coolant vapor is cooled and condensed by wind caused by vehiclerunning or draft from condenser fan 42 or the radiator fan for enginecooling. The coolant liquid liquefied in heat exchanger 14 returns tocooling unit 30 sequentially through coolant passages 22 and 33,electronic expansion valve 38, and coolant passage 34.

In this way, the looped route extending through cooling unit 30 and heatexchanger 14 forms a heat pipe including HV equipment 31 as a heatingunit and heat exchanger 14 as a cooling unit. Therefore, when vaporcompression refrigeration cycle 10 is stopped, that is, even whencooling for the vehicle is stopped, HV equipment 31 can be reliablycooled without having to start compressor 12. HV equipment 31 can becooled without having to use the motive power of compressor 12, andcompressor 12 does not need to be continuously operated for cooling HVequipment 31. Accordingly, the power consumption of compressor 12 can bereduced to allow improvement in fuel efficiency of the vehicle and alsoallow extension of the operating life of compressor 12, so that thereliability of compressor 12 can be improved.

FIG. 9 shows a ground surface 60. Cooling unit 30 is disposed below heatexchanger 14 as seen in the vertical direction perpendicular to groundsurface 60. In the looped route through which the coolant circulatesbetween heat exchanger 14 and cooling unit 30, cooling unit 30 isdisposed in the lower portion while heat exchanger 14 is disposed in theupper portion. Heat exchanger 14 is disposed at the position higher thancooling unit 30.

In this case, the coolant vapor heated and evaporated in cooling unit 30rises through the looped route and reaches heat exchanger 14. Then, thiscoolant vapor is cooled and condensed in heat exchanger 14, and turnsinto a liquid coolant, which then goes down through the looped route bythe action of gravity, and returns to cooling unit 30. In other words, athermosyphon-type heat pipe is formed of cooling unit 30, heat exchanger14, and a coolant route connecting them. The heat transfer efficiencyfrom HV equipment 31 to heat exchanger 14 can be improved by forming aheat pipe. Accordingly, even when vapor compression refrigeration cycle10 is stopped, HV equipment 31 can be more efficiently cooled withoutapplying motive power.

Cooling device 1 in the second embodiment further includes a check valve54. Check valve 54 is disposed in coolant passage 21 between compressor12 and heat exchanger 14 on the side closer to compressor 12 than to theconnection portion between coolant passage 21 and communication passage51. Check valve 54 allows the coolant to flow from compressor 12 towardheat exchanger 14, but inhibits the coolant from flowing in thedirection opposite thereto. In this way, it becomes possible to reliablyform a closed-loop coolant route through which the coolant is circulatedbetween heat exchanger 14 and cooling unit 30 during the heat pipeoperation mode shown in FIGS. 8 and 9.

If check valve 54 is not provided, the coolant may flow fromcommunication passage 51 into coolant passage 21 on the compressor 12side. By providing check valve 54, the flow of the coolant flowing fromcommunication passage 51 toward compressor 12 can be reliably inhibited.Accordingly, the cooling ability for HV equipment 31 using a heat pipeformed by a looped coolant route can be prevented from decreasing whilevapor compression refrigeration cycle 10 is stopped. Therefore, HVequipment 31 can be efficiently cooled also when cooling for the vehiclecabin is stopped.

Furthermore, when the amount of the coolant within the closed-loopcoolant route becomes insufficient while vapor compression refrigerationcycle 10 is stopped, compressor 12 is operated only for a short timeperiod, so that the coolant can be supplied through check valve 54 intothe closed-loop route. Consequently, the amount of the coolant withinthe closed loop can be increased to increase the heat exchangeprocessing amount in the heat pipe. Therefore, since the amount of thecoolant in the heat pipe can be ensured, it becomes possible to avoidinsufficient cooling of HV equipment 31 resulting from shortage of thecoolant amount.

FIG. 10 is a schematic diagram showing cooling device 1 in the casewhere the required cooling performance for HV equipment 31 is raisedwhile the air conditioner is operated. FIG. 10 shows the case where theair conditioner for cooling the vehicle cabin is being operated, and thecase where improvement in cooling performance for HV equipment 31 isrequired because the heat amount generated from HV equipment 31 isincreased, for example, such as the case where the driver operating thevehicle selects a sport driving mode and HV equipment 31 is operated ina highly loaded state.

The “air-conditioner ON/low-temperature coolant cooling operation mode”of the operation modes shown in FIG. 7 is an operation mode shown inFIG. 10 in which the air conditioner for cooling the vehicle cabin isbeing operated and improvement in the ability to cool HV equipment 31 isrequired. In this case, as with the state shown in FIG. 6, compressor 12is in the operated state and the opening degree of flow rate regulatingvalve 28 is adjusted. In contrast, electronic expansion valve 38 isnarrowed such that its opening degree is decreased. Switching valve 52is switched to be opened or closed so as to allow communication betweencoolant passage 35 and bypass route 41, and to disallow coolant passage36 and communication passage 51 to be in communication with both ofcoolant passage 35 and bypass route 41.

In this case, the coolant flowing through cooling unit 30 and used forcooling HV equipment 31 flows through switching valve 52 into bypassroute 41, and flows into gas-liquid separator 40 on the upstream side ofcompressor 12. The coolant for cooling HV equipment 31 flows fromcooling unit 30 through gas-liquid separator 40 into compressor 12, butdoes not flow into heat exchanger 15, expansion valve 16 and heatexchanger 18. Bypass route 41 is directly connected to switching valve52 and gas-liquid separator 40, and provided as a coolant routebypassing heat exchanger 15, expansion valve 16 and heat exchanger 18.

Since the coolant flows into the route including expansion valve 16 andheat exchanger 18 by adjusting the opening degree of flow rateregulating valve 28, the low-temperature and low-pressure coolant thathas been subjected to throttle expansion in expansion valve 16 issupplied to heat exchanger 18. Thereby, heat exchange is performed inheat exchanger 18 between the air-conditioning air for cooling thevehicle cabin and the coolant, thereby allowing the air-conditioning airto be cooled, so that the cooling ability can be ensured. As the coolantfor cooling HV equipment 31 flows from cooling unit 30 through bypassroute 41 toward the inlet of compressor 12, the ability to cool HVequipment 31 can be raised to allow efficient cooling of HV equipment31. Therefore, the cooling performance suitable for the amount of heatgenerated from HV equipment 31 can be achieved.

It is to be noted that the operation state of cooling device 1 that hasbeen described with reference to FIG. 3 in the first embodimentcorresponds to this “air-conditioner ON/low-temperature coolant coolingoperation mode”.

FIG. 11 is a schematic diagram showing cooling device 1 in the casewhere the required cooling performance for HV equipment 31 is raisedwhile the air conditioner is stopped. FIG. 11 shows the case where theair conditioner is being stopped and the case where improvement incooling performance for HV equipment 31 is required because the heatamount generated from HV equipment 31 is increased.

The “air-conditioner OFF/low-temperature coolant cooling operation mode”of the operation modes shown in FIG. 7 is an operation mode shown inFIG. 11, in which the air conditioner for cooling the vehicle cabin isbeing stopped, and improvement in the ability to cool HV equipment 31 isrequired. In this case, flow rate regulating valve 28 is fully closed(the opening degree is 0%). Electronic expansion valve 38 is narrowedsuch that its opening degree is decreased. Switching valve 52 isswitched to be opened or closed so as to allow communication betweencoolant passage 35 and bypass route 41, and to disallow coolant passage36 and communication passage 51 to be in communication with both ofcoolant passage 35 and bypass route 41. Compressor 12 is brought into anoperated state in order to provide driving force that allows the coolantto circulate through the refrigeration cycle via bypass route 41. Thecoolant flowing through cooling unit 30 flows through switching valve 52into bypass route 41, and further into gas-liquid separator 40.

The coolant for cooling HV equipment 31 flows from cooling unit 30through bypass route 41 toward the inlet of compressor 12, therebyimproving the ability to cool HV equipment 31, so that HV equipment 31can be efficiently cooled. Consequently, the cooling performancesuitable for the amount of heat generated from HV equipment 31 can beachieved. It is to be noted that the operation state of cooling device 1that has been described with reference to FIG. 4 in the first embodimentcorresponds to this “air-conditioner OFF/low-temperature coolant coolingoperation mode”.

According to cooling device 1 in the second embodiment, as in the firstembodiment, the flow of the coolant flowing through bypass route 41 isselected when the amount of heat generated from HV equipment 31 isincreased, thereby allowing formation of a flow of the coolant flowingfrom cooling unit 30 through bypass route 41 into gas-liquid separator40. In accordance with an increase in the amount of heat generated fromHV equipment 31, the ability to cool HV equipment 31 can be enhanced,and the cooling performance suitable for the amount of heat generatedfrom HV equipment 31 can be achieved. When the amount of heat generatedfrom HV equipment 31 is increased, the low-temperature coolant that hasbeen turned into a mist state by throttle expansion for this coolant inelectronic expansion valve 38 is supplied to cooling unit 30, therebyallowing a further increase in the amount of heat exchange between thecoolant and HV equipment 31. Accordingly, the ability to cool HVequipment 31 can be further improved.

Furthermore, by providing communication passage 51, a looped route canbe formed, through which the coolant is circulated between cooling unit30 and heat exchanger 14 through communication passage 51 but notthrough compressor 12. The coolant can be circulated through this loopedroute to flow between heat exchanger 14 and cooling unit 30 withoutoperating compressor 12. Since HV equipment 31 can be reliably cooledeven in the state where the motive power for circulation of the coolantis not supplied from compressor 12, the motive power required forcooling HV equipment 31 can be reduced.

Hereinafter described will be control of cooling device 1 according tothe second embodiment. FIG. 12 is a block diagram showing details of theconfiguration of a control unit 80. Control unit 80 shown in FIG. 12includes an ECU (Electric Control Unit) 81 controlling cooling device 1.ECU 81 receives a signal from an air-conditioner switch 82 indicatingthat the air conditioner is ON or OFF. Air-conditioner switch 82 isprovided, for example, on the instrument panel in the forward partwithin the vehicle cabin. By the vehicle occupant operatingair-conditioner switch 82, the air conditioner is switched between ONand OFF to start or stop cooling of the vehicle cabin.

From a sport driving mode selection switch 83, ECU 81 receives a signalindicating whether the vehicle is set in the normal driving mode and thesport driving mode. Sport driving mode selection switch 83 is provided,for example, on the instrument panel in the forward part within thevehicle cabin. When the vehicle occupant operates sport driving modeselection switch 83, the normal driving mode or the sport driving modeis selected.

ECU 81 receives a signal indicating a temperature from a temperatureinput unit 84. Temperature input unit 84 receives an input of thetemperature of the coolant at the inlet and outlet of cooling unit 30from the sensor detecting the temperature of the coolant flowing intocooling unit 30 and the temperature of the coolant flowing out ofcooling unit 30. Temperature input unit 84 may also receive an input ofthe temperature of the outside air near cooling device 1 and thetemperature of the air-conditioning air that is adjusted by heatexchange in heat exchanger 18.

Control unit 80 also includes a compressor control unit 85 controllingcompressor 12 to be started and stopped; a motor control unit 86controlling the rotation speed of motor 44; and a valve control unit 87controlling flow rate regulating valve 28, electronic expansion valve 38and switching valve 52 to be opened and closed. Control unit 80 alsoincludes a memory 89 such as an RAM (Random Access Memory) and an ROM(Read Only Memory). Cooling device 1 is controlled by ECU 81 executingvarious processes in accordance with the control program stored inmemory 89.

Compressor control unit 85 receives a control instruction transmittedfrom ECU 81, and transmits a signal C1 to compressor 12 that instructscompressor 12 to be started or stopped. Valve control unit 87 receives acontrol instruction transmitted from ECU 81, transmits a signal V1 toflow rate regulating valve 28 that gives an instruction for the openingdegree of flow rate regulating valve 28, transmits a signal V2 toelectronic expansion valve 38 that gives an instruction for the openingdegree of electronic expansion valve 38, and transmits a signal V3 toswitching valve 52 that gives an instruction for setting switching valve52 to be opened or closed. Motor control unit 86 receives a controlinstruction transmitted from ECU 81, and transmits a signal M1 to motor44 that gives an instruction for the rotation speed of motor 44.

Based on whether the air conditioner is ON or OFF, based on whether thesport driving mode is selected or not, and based on various temperaturesinput into temperature input unit 84, ECU 81 controls start anddiscontinuation of the operation of compressor 12, the rotation speed ofmotor 44, the opening degrees of flow rate regulating valve 28 andelectronic expansion valve 38, and the setting for opening or closing ofswitching valve 52. ECU 81 has a function as operation mode switchingmeans for switching the operation mode of cooling device 1.

When the rotation speed of motor 44 is changed, the amount of heatexchange between the coolant and outside air in heat exchanger 14 iscontrolled. When the rotation speed of motor 44 is increased to increasethe rotation speed of condenser fan 42, the flow rate of the airsupplied to heat exchanger 14 is increased and the amount of heatexchange between the coolant and the outside air in heat exchanger 14 isincreased. Consequently, the coolant cooling ability of heat exchanger14 is improved. When the rotation speed of motor 44 is decreased todecrease the rotation speed of condenser fan 42, the flow rate of theair supplied to heat exchanger 14 is decreased and the amount of heatexchange between the coolant and the outside air in heat exchanger 14 isdecreased. Consequently, the coolant cooling ability of heat exchanger14 is decreased.

FIG. 13 is a flowchart illustrating an example of a method ofcontrolling cooling device 1. As shown in FIG. 13, when cooling of HVequipment 31 serving as a heat source is started using cooling device 1,it is first determined in step (S 10) whether cooling of the heat sourceis ended or not. If it is determined that cooling is not ended, it isdetermined in step (S20) whether the sport driving mode is selected ornot by operation of sport driving mode selection switch 83.

As described above, the amount of heat generated from HV equipment 31increases in the sport driving mode as compared with the normal drivingmode. In step (S20), it is determined whether the sport driving mode isselected or not, thereby determining whether the amount of heatgenerated by HV equipment 31 is increased or decreased. When theintermediate value between the amount of generated heat from HVequipment 31 in the normal driving mode and the amount of generated heatfrom HV equipment 31 in the sport driving mode is set as a thresholdvalue of the amount of generated heat, the amount of generated heat fromHV equipment 31 at the time when the sport driving mode is selected isequal to or greater than the threshold value, and the amount ofgenerated heat from HV equipment 31 at the time when the normal drivingmode is selected is equal to or less than the threshold value.

In the case where it is determined in step (S20) that the sport drivingmode is ON, that is, in the case where the sport driving mode isselected by operation of sport driving mode selection switch 83 and theamount of generated heat from HV equipment 31 is increased, it isdetermined in step (S30) whether the air conditioner is ON or not.Compressor 12 is being operated if the air conditioner is ON. Compressor12 is being stopped if the air conditioner is OFF. When it is determinedin step (S30) that the air conditioner is ON, the process proceeds tostep (S40), where cooling device 1 cools HV equipment 31 in theair-conditioner ON/low-temperature coolant cooling operation mode.

At this time, the air conditioner is ON, and compressor 12 is started inorder to cause the coolant to circulate through the entire vaporcompression refrigeration cycle 10. Accordingly, compressor control unit85 transmits signal C1 to compressor 12 for maintaining the operation ofcompressor 12. Valve control unit 87 transmits signal V1 to flow rateregulating valve 28 for adjusting the opening degree of flow rateregulating valve 28 so as to cause sufficient coolant to flow intocooling unit 30, transmits signal V2 to electronic expansion valve 38for decreasing the opening degree of electronic expansion valve 38, andtransmits signal V3 to switching valve 52 for switching between openingand closing of switching valve 52 so as to allow coolant passage 35 tobe in communication with bypass route 41.

Since the coolant flows into the route including expansion valve 16 andheat exchanger 18 by adjusting the opening degree of flow rateregulating valve 28, the low-temperature and low-pressure coolant thathas been subjected to throttle expansion in expansion valve 16 issupplied to heat exchanger 18. This allow heat exchange between theair-conditioning air for cooling the vehicle cabin and the coolant inheat exchanger 18, thereby allowing the air-conditioning air to becooled, so that the ability to cool the vehicle cabin can be ensured.The coolant decreased in temperature by throttle expansion in electronicexpansion valve 38 by adjusting the opening degree of electronicexpansion valve 38 is caused to flow through cooling unit 30, to performheat exchange between the coolant flowing through cooling passage 32 andHV equipment 31, thereby cooling HV equipment 31. The coolant that hascooled HV equipment 31 flows from cooling unit 30 through bypass route41 toward the inlet of compressor 12. Consequently, since the ability tocool HV equipment 31 can be enhanced to allow efficient cooling of HVequipment 31, cooling performance suitable for the amount of generatedheat from HV equipment 31 can be achieved.

After that, the control flow is returned to step (S 10), where it isdetermined whether cooling of the heat source is ended or not.

When it is determined in step (S30) that the air conditioner is OFF, theprocess proceeds to step (S50), and compressor 12 is started. Since theair conditioner is OFF and compressor 12 is stopped, compressor controlunit 85 at this time transmits signal C1 for starting compressor 12 tocompressor 12.

Then, in step (S60), cooling device 1 cools HV equipment 31 in theair-conditioner OFF/low-temperature coolant cooling operation mode.Valve control unit 87 transmits signal V1 to flow rate regulating valve28 for fully closing flow rate regulating valve 28, transmits signal V2to electronic expansion valve 38 for decreasing the opening degree ofelectronic expansion valve 38, and transmits signal V3 to switchingvalve 52 for switching between opening and closing of switching valve 52so as to allow coolant passage 35 to be in communication with bypassroute 41.

Since the air conditioner is OFF, it is not necessary to cause thecoolant to flow through heat exchanger 18. Accordingly, flow rateregulating valve 28 is fully closed, to stop the flow of the coolanttoward the route including expansion valve 16 and heat exchanger 18. Thecoolant decreased in temperature by throttle expansion in electronicexpansion valve 38 by adjusting the opening degree of electronicexpansion valve 38 is caused to flow through cooling unit 30, to performheat exchange between the coolant flowing through cooling passage 32 andHV equipment 31, thereby cooling HV equipment 31. The coolant havingcooled HV equipment 31 flows from cooling unit 30 through bypass route41 toward the inlet of compressor 12. Consequently, since the ability tocool HV equipment 31 can be enhanced to allow efficient cooling of HVequipment 31, cooling performance suitable for the amount of heatgenerated from HV equipment 31 can be achieved.

After that, the control flow is returned to step (S 10), where it isdetermined whether cooling of the heat source is ended or not.

When it is determined in step (S20) that the sport driving mode is OFF,that is, the normal driving mode is selected by operation of sportdriving mode selection switch 83, it is determined in step (S70) whetherthe air conditioner is ON or not. When it is determined in step (S70)that the air conditioner is ON, the process proceeds to step (S90),where cooling device 1 cools HV equipment 31 in the air-conditioneroperation mode.

When it is determined in step (S70) that the air conditioner is OFF, itis determined in step (S80) whether cooling of the heat source in theair-conditioner operation mode is required or not. For example, based onthe detection value of the temperature input into temperature input unit84, it can be determined whether cooling in the air-conditioneroperation mode is required or not. Specifically, when the outlettemperature of cooling unit 30 exceeds the inlet temperature thereof,when the outside air temperature is higher than a prescribed temperature(for example, 25° C.), when the temperature of the air-conditioning airis higher than a prescribed temperature (for example, 20° C.), or thelike, it is determined that the cooling ability in cooling unit 30 isdeteriorated, and the control instruction for starting compressor 12 canbe transmitted to compressor control unit 85.

Alternatively, also when the vehicle runs in the circumstance where theamount of generated heat from HV equipment 31 is increased, for example,such as in the state where the vehicle runs on a climbing road, HVequipment 31 may be cooled in the air-conditioner operation mode. Theability of cooling device 1 to cool HV equipment 31 is relativelygreater in the air-conditioner operation mode in which compressor 12 isoperated than in the heat pipe operation mode. Accordingly, by operatingcooling device 1 in the air-conditioner operation mode to cool HVequipment 31, overheating of HV equipment 31 can be reliably prevented.When it is determined that cooling of the heat source in theair-conditioner operation mode is required, the process proceeds to step(S90), where cooling device 1 cools HV equipment 31 in theair-conditioner operation mode.

In this case, compressor control unit 85 transmits signal C1 tocompressor 12 that instructs compressor 12 to be started. Valve controlunit 87 transmits signal V1 to flow rate regulating valve 28 foradjusting the opening degree of flow rate regulating valve 28 so as toallow sufficient coolant to flow into cooling unit 30, transmits signalV2 to electronic expansion valve 38 for fully opening electronicexpansion valve 38, and transmits signal V3 to switching valve 52 forswitching between opening and closing of switching valve 52 so as toallow coolant passage 35 to be in communication with coolant passage 36.

Since the coolant flows through the route including expansion valve 16and heat exchanger 18 by adjusting the opening degree of flow rateregulating valve 28, the low-temperature and low-pressure coolant thathas been subjected to throttle expansion in expansion valve 16 issupplied to heat exchanger 18. This allow heat exchange between theair-conditioning air for cooling the vehicle cabin and the coolant inheat exchanger 18, thereby allowing the air-conditioning air to becooled, so that the ability to cool the vehicle cabin can be ensured.Furthermore, by adjusting the opening degree of flow rate regulatingvalve 28, a sufficient amount of the coolant for cooling HV equipment 31flows through cooling unit 30. Consequently, the coolant having beenheat-exchanged with the outside air and cooled in heat exchanger 14 iscaused to flow through cooling unit 30, to perform heat exchange betweenthe coolant flowing through cooling passage 32 and HV equipment 31, sothat HV equipment 31 can be cooled.

After that, the control flow is returned to step (S 10), where it isdetermined whether cooling of the heat source is ended or not.

When it is determined in step (S80) that cooling of the heat source inthe air-conditioner operation mode is not required, cooling device 1cools the heat source in the heat pipe operation mode in step (S100).Since the air conditioner is OFF in this case, compressor 12 is in thestopped state. Accordingly, compressor control unit 85 transmits signalC1 to compressor 12 for maintaining compressor 12 in the stopped state.Valve control unit 87 transmits signal V1 to flow rate regulating valve28 for fully closing flow rate regulating valve 28, transmits signal V2to electronic expansion valve 38 for fully opening electronic expansionvalve 38, and transmits signal V3 to switching valve 52 for switchingbetween opening and closing of switching valve 52 so as to allow coolantpassage 35 to be in communication with communication passage 51.

Consequently, a looped route is formed, through which the coolant iscirculated between cooling unit 30 and heat exchanger 14, therebyforming a thermosyphon-type heat pipe. The liquid-phase coolant cooledin heat exchanger 14 is caused to flow through cooling unit 30 by theaction of gravity, to perform heat exchange between the coolant flowingthrough cooling passage 32 and HV equipment 31, thereby cooling HVequipment 31. The coolant vapor that has been heated and evaporated incooling unit 30 rises through the looped route and reaches heatexchanger 14 again.

After that, the control flow is returned to step (510), where it isdetermined whether cooling of the heat source is ended or not.

If it is determined in step (S 10) that cooling of the heat source isended, supply of the coolant to cooling unit 30 is stopped, to stopcooling of HV equipment 31.

As described above, cooling device 1 in the second embodiment can coolHV equipment 31 serving as a heat source in both of the “air-conditioneroperation mode” and the “heat pipe operation mode” based on theoperation state of the air conditioner when the sport driving mode isnot selected. Since HV equipment 31 can be reliably cooled withouthaving to start compressor 12 in the heat pipe operation mode,compressor 12 does not need to be continuously operated for cooling HVequipment 31. Accordingly, the power consumption of compressor 12 can bereduced to allow improvement in fuel efficiency of the vehicle and alsoallow extension of the operating life of compressor 12, so that thereliability of compressor 12 can be improved.

Switching valve 52 is controlled to be opened or closed in accordancewith start or discontinuation of the operation of compressor 12 forswitching the operation mode of cooling device 1. Thereby, switchingbetween the air-conditioner operation mode and the heat pipe operationmode can be reliably performed, and the coolant can flow through anappropriate route for each operation mode.

The operation mode of cooling device 1 can be switched by the occupantof an electric vehicle manually operating a control panel to switch theair conditioner to be turned ON/OFF. When the air conditioning withinthe vehicle cabin is not required, the vehicle occupant turns the airconditioner to be OFF. Thereby, the operation mode of cooling device 1is switched such that HV equipment 31 is cooled in the heat pipeoperation mode. When the heat pipe operation mode is selected,compressor 12 is stopped. Accordingly, the operation time period ofcompressor 12 can be further shortened. Consequently, the effects ofreducing the power consumption of compressor 12 and improving thereliability of compressor 12 can be achieved more remarkably.

Alternatively, when the sport driving mode is selected, Hy equipment 31serving as a heat source can be cooled in the “air-conditionerON/low-temperature coolant cooling operation mode” or in the“air-conditioner OFF/low-temperature coolant cooling operation mode”.When the sport driving mode is selected and the amount of generated heatfrom HV equipment 31 is increased, the flow of the coolant flowingthrough bypass route 41 is selected by switching valve 52, to form aflow of the coolant flowing from cooling unit 30 through bypass route 41into gas-liquid separator 40. Consequently, the ability to cool HVequipment 31 can be enhanced, and cooling performance suitable for theamount of generated heat from HV equipment 31 can be achieved. Thecoolant is subjected to throttle expansion in electronic expansion valve38 on the upstream side of cooling unit 30 to lower the temperature ofthe coolant flowing through cooling unit 30, thereby allowing furtherimprovement in the ability to cool HV equipment 31.

In the above-described embodiments, explanations have been given withregard to cooling device 1 cooling electrical devices mounted in thevehicle by referring to HV equipment 31 as an example. The electricaldevices may be any electrical devices as long as they are at leastoperated to generate heat, but are not limited to exemplified electricdevices such as an inverter and a motor generator. In the case where aplurality of electrical devices need to be cooled, it is desirable thatthese plurality of electrical devices have a common targeted temperaturerange for cooling. The targeted temperature range for cooling is anappropriate temperature range as a temperature environment whereelectrical devices are operated.

Furthermore, the heat source cooled by cooling device 1 of the presentinvention is not limited to electrical devices mounted in the vehicle,but may be any devices generating heat, or a part of any devicesgenerating heat.

Although the embodiments of the present invention have been described asabove, it should be understood that the embodiments disclosed herein areillustrative and non-restrictive in every respect. The scope of thepresent invention is defined by the terms of the claims, rather than thedescription above, and is intended to include any modifications withinthe meaning and scope equivalent to the terms of the claims.

INDUSTRIAL APPLICABILITY

The cooling device according to the present invention may beparticularly advantageously applied to cooling of an electrical deviceby using a vapor compression refrigeration cycle for cooling a vehiclecabin in a vehicle such as an electric vehicle equipped with electricaldevices such as a motor generator, an inverter and a battery.

REFERENCE SIGNS LIST

1 cooling device, 10 vapor compression refrigeration cycle, 12compressor, 14, 15, 18 heat exchanger, 16 expansion valve, 21, 22, 23,24, 25, 26, 27, 33, 34, 35, 36 coolant passage, 28 flow rate regulatingvalve, 30 cooling unit, 31 HV equipment, 32 cooling passage, 38electronic expansion valve, 40 gas-liquid separator, 41 bypass route, 42condenser fan, 51 communication passage, 52 switching valve, 80 controlunit, 81 ECU, 82 air-conditioner switch, 83 sport driving mode selectionswitch, 84 temperature input unit, 85 compressor control unit, 87 valvecontrol unit.

1. A cooling device cooling a heat source, said cooling devicecomprising: a compressor for circulating a coolant; a first heatexchanger performing heat exchange between said coolant and outside air;a decompressing said coolant; a second heat exchanger performing heatexchange between said coolant and air-conditioning air; a cooling unitprovided on a route of said coolant flowing between said first heatexchanger and said decompressor, and cooling said heat source using saidcoolant; a bypass route bypassing said decompressor and said second heatexchanger; and a route selection unit selectively switching between aflow of said coolant flowing from said cooling unit toward saiddecompressor and a flow of said coolant flowing through said bypassroute, said route selection unit selecting the flow of said coolantflowing through said bypass route when an amount of generated heat bysaid heat source is increased.
 2. The cooling device according to claim1, comprising a temperature lowering unit lowering a temperature of saidcoolant, wherein said temperature lowering unit lowers the temperatureof said coolant flowing through said cooling unit when said routeselection unit selects the flow of said coolant flowing through saidbypass route.
 3. The cooling device according to claim 2, comprising anelectronic expansion valve provided on a route of said coolant flowingbetween said first heat exchanger and said cooling unit.
 4. The coolingdevice according to claim 1, comprising a gas-liquid separator providedon a route of said coolant flowing between said second heat exchangerand said compressor, wherein said coolant flowing from said cooling unitthrough said bypass route flows into said gas-liquid separator. 5.(canceled)
 6. The cooling device according to claim 1, comprising acommunication passage allowing communication between a route of saidcoolant flowing between said compressor and said first heat exchanger,and a route of said coolant flowing between said cooling unit and saiddecompressor.
 7. The cooling device according to claim 6, wherein saidroute selection unit can form a flow of said coolant flowing from saidcooling unit toward said communication passage.
 8. A method ofcontrolling a cooling device cooling a heat source, said cooling deviceincluding a compressor for circulating a coolant, a first heat exchangerperforming heat exchange between said coolant and outside air, adecompressing said coolant, a second heat exchanger performing heatexchange between said coolant and air-conditioning air, a cooling unitprovided on a route of said coolant flowing between said first heatexchanger and said decompressor, and cooling said heat source using saidcoolant, a bypass route bypassing said decompressor and said second heatexchanger, and a route selection unit selectively switching between aflow of said coolant flowing from said cooling unit toward saiddecompressor and a flow of said coolant flowing through said bypassroute, said method comprising: the step of determining an amount ofgenerated heat by said heat source; and the step of cooling said heatsource by forming the flow of said coolant flowing through said bypassroute when it is determined in said step of determining an amount ofgenerated heat that the amount of generated heat is equal to or higherthan a threshold value.
 9. The method of controlling a cooling deviceaccording to claim 8, wherein said cooling device includes an electronicexpansion valve provided on a route of said coolant flowing between saidfirst heat exchanger and said cooling unit, and in said step of coolingsaid heat source, an opening degree of said electronic expansion valveis decreased to cool said heat source.
 10. The method of controlling acooling device according to claim 8, comprising: the step of determiningan operation state of said compressor when it is determined in said stepof determining an amount of generated heat that the amount of generatedheat is equal to or higher than the threshold value; and the step ofstarting said compressor when it is determined in said step ofdetermining an operation state that said compressor is being stopped.11. The cooling device according to claim 2, comprising a gas-liquidseparator provided on a route of said coolant flowing between saidsecond heat exchanger and said compressor, wherein said coolant flowingfrom said cooling unit through said bypass route flows into saidgas-liquid separator.
 12. The cooling device according to claim 2,comprising a communication passage allowing communication between aroute of said coolant flowing between said compressor and said firstheat exchanger, and a route of said coolant flowing between said coolingunit and said decompressor.
 13. The cooling device according to claim12, wherein said route selection unit can form a flow of said coolantflowing from said cooling unit toward said communication passage. 14.The cooling device according to claim 3, comprising a gas-liquidseparator provided on a route of said coolant flowing between saidsecond heat exchanger and said compressor, wherein said coolant flowingfrom said cooling unit through said bypass route flows into saidgas-liquid separator.
 15. The cooling device according to claim 3comprising a communication passage allowing communication between aroute of said coolant flowing between said compressor and said firstheat exchanger, and a route of said coolant flowing between said coolingunit and said decompressor.
 16. The cooling device according to claim15, wherein said route selection unit can form a flow of said coolantflowing from said cooling unit toward said communication passage. 17.The cooling device according to claim 4, comprising a communicationpassage allowing communication between a route of said coolant flowingbetween said compressor and said first heat exchanger, and a route ofsaid coolant flowing between said cooling unit and said decompressor.18. The cooling device according to claim 17, wherein said routeselection unit can form a flow of said coolant flowing from said coolingunit toward said communication passage.
 19. The method of controlling acooling device according to claim 9, comprising: the step of determiningan operation state of said compressor when it is determined in said stepof determining an amount of generated heat that the amount of generatedheat is equal to or higher than the threshold value; and the step ofstarting said compressor when it is determined in said step ofdetermining an operation state that said compressor is being stopped.